Objective To investigate the regulatory effect of calcitonin gene-related peptide (CGRP) on the mRNA and protein expression of neuronal nitric oxide synthase (NOS), as well as the release of nitric oxide (NO) in cultured human keratinocyte line HaCaT. Methods NO level in the supernatant of cell culture medium was detected with an enzymatic NO detecting kit, the mRNA expression of neuronal NOS was studied with reverse transcription polymerase chain reaction(RT-PCR), and the protein expression of neuronal NOS was studied with immunochemical technique(SP). Results Compared with that in normal culture condition, the mRNA and protein expression of neuronal NOS and the release of NO was significantly upregulated by CGRP in HaCaT cells. Whereas, the expression of neuronal NOS and the release of NO in HaCaT cells induced by CGRP was inhibited by CGRP-8-37, an inhibitor of CGRP receptor. Conclusion The expression of neuronal NOS in keratinocytes and the release of NO from keratinocytes could be upregulated by CGRP.